diff --git a/NT/tools/rntcl b/NT/tools/rntcl
index a930d8ef3019261d80f37e99d9f2141b4a61f277..d94f5427f36826df68512c98f86869f9e0fc188f 100755
--- a/NT/tools/rntcl
+++ b/NT/tools/rntcl
@@ -47,6 +47,7 @@ int main(int argc, string *argv)
     "-D__WIN32__",
     "-D_WIN32",
     "-D__NT__",
+    "-D__STDC__",
     "-nologo",
   });
 
@@ -196,10 +197,9 @@ int main(int argc, string *argv)
       break;
 
     case "obj":
-      if(output)
-	cflags+=({"-Fo"+fixpath(output)});
-      else
-	output=remove_ext(argv[1])+".obj";
+      if(!output)
+	output=remove_ext(argv[1])+".o";
+      cflags+=({"-Fo"+fixpath(output)});
       wantfile=output;
       break;